This invention relates to packing elements use in mass transfer and direct heat transfer applications and specifically to packing elements of a generally cylindrical shape, such as for example Pall and Lessing rings.
Such elements are used in reactors where liquids and gases are contacted so as to bring about a reaction, heat transfer, solution or dissolution operations by intimately contacting two flowing fluids. As a consequence they have shapes designed to maximize surface area while retaining dimensional stability such they they do not collapse or become crushed during use. One means of achieving this end is to form the rings from cylindrical metal blanks, and providing internal structure by a variety of suitable techniques.
It is however desirable to have a structure that is easily produced to a standard design in large volumes. To satisfy these requirements the elements are often stamped out of a flat metal plate intended to be bent into a cylindrical shape with a plurality of flaps cut from the plate and bent inwards towards the axis of the cylinder. This is the shape of the typical Pall ring and is described for example in U.S. Pat. No. Re. 27,217. Another type of ring is the so-called Lessing ring in which a metal strip is bent into a cylindrical shape and one end of the strip is bent inwardly along a chord of the cross-section of the cylinder.
In order to retain the rigidity of such a ring it needs to be shaped from a relatively thick metal plate that will have be able to withstand the compressive forces encountered in use. Lacking such rigidity the rings will become compressed under the loading in the tower and more rings will be needed to fill the tower. In addition compressed rings do not have the same performance characteristics such that some predictability in operation is lost.
On the other hand it is desirable to reduce the thickness of this metal plate to save weight and to make the rings less expensive.
One solution has been to use a pair of bridging members to hold two cooperating semicylindrical pieces together as is described in U.S. Pat. No. 4,197,264. This has a significant disadvantage in that the production process requires the combination of four separate components to make the final product.
The present invention provides a metal strip that can be used to form a relatively rigid packing of the Pall or Lessing ring type while allowing the use of thinner gauge metal. The strip is so designed that it can be made into a packing element of the above type in a simple bending operation readily adapted to the use of mass production techniques.